BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a catalyst composition and method of using the same
for the oxidation of oxidizable components of exhaust gases, and more specifically
to the treatment of diesel exhaust to reduce the content of particulates and other
pollutants discharged to the atmosphere.
Description of Related Art
[0002] Diesel engine exhaust is a heterogeneous material which contains not only gaseous
pollutants such as carbon monoxide ("CO") and unburned hydrocarbons ("HC"), but also
soot particles which comprise both a dry, solid carbonaceous fraction and a soluble
organic fraction. The soluble organic fraction is sometimes referred to as a volatile
organic fraction ("VOF"), which terminology will be used herein. The VOF may exist
in diesel exhaust either as a vapor or as an aerosol (fine droplets of liquid condensate)
depending on the temperature of the diesel exhaust.
[0003] Oxidation catalysts comprising a platinum group metal dispersed on a refractory metal
oxide support are known for use in treating the exhaust of diesel engines in order
to convert both HC and CO gaseous pollutants and particulates, i.e., soot particles,
by catalyzing the oxidation of these pollutants to carbon dioxide and water. One problem
faced in the treatment of diesel engine exhaust is presented by the presence of sulfur
in diesel fuel. Upon combustion, sulfur forms sulfur dioxide and the oxidation catalyst
catalyzes the SO
2 to
3 SO ("sulfates") with subsequent formation of condensable sulfur compounds, such as
sulfuric acid, which condense upon, and thereby add to, the mass of particulates.
The sulfates also react with activated alumina supports to form aluminum sulfates,
which render activated alumina-containing catalysts inactive as disclosed in U.S.
Patent 4,171,289. Previous attempts to deal with the sulfation problem include the
incorporation of large amounts of sulfate-resistant materials such as vanadium oxide
into the support coating, or the use of sulfur-resistant support materials such as
α-alumina (alpha), silica and titania.
[0004] The prior art also shows an awareness of the use of zeolites, including metal-doped
zeolites (i.e. catalytically active), to treat diesel exhaust. For example, U.S. Patent
4,929,581 discloses a filter for diesel exhaust, in which the exhaust is constrained
to flow through the catalyst walls to filter the soot particles. A catalyst comprising
a platinum group metal-doped zeolite is dispersed on the walls of the filter to catalyze
oxidation of the soot to unplug the filter.
[0005] EPO 92/102161.4 discloses a catalyst for reducing the particle content and/or size
in diesel engine exhaust by way of the zeolitic catalyst having acidic properties.
The catalyst is stated to have properties enabling it to crack long-chain aromatic
hydrocarbons. Zeolites include faujasite, pentasil and mordenite. Additionally, the
faujasite and mordenite can be de-aluminated. The zeolite is stated to contain one
or several transition elements which can include copper, nickel, cobalt, iron, chromium,
manganese and/or vanadium.
[0006] Japanese Application No. S63-95026 (Publication No. H1-266854, October 24, 1989)
discloses a catalyst for cleansing exhaust gas. The catalyst consists of zeolite,
ion-exchanged with copper and carried on a fireproof carrier. The ion-exchange site
is on the surface of the zeolite supercage and the coordination site of the oxygen
atom for copper ion is a four-coordinate square.
[0007] Iwamoto, Catalytic Decomposition of Nitrogen Oxides, Petrotech
12, 888-893, 1989 is directed to the reduction of nitrogen oxides and various emissions
from diesel exhaust. It is taught to use copper ion-exchanged ZSM-5 or mordanite or
ferrierite. U.S. Patent No. 4,934,142 discloses an exhaust emission control device
comprising a first filter provided in an exhaust system of an engine to collect particulates
contained in an exhaust gas. A second filter is provided downstream of the first filter
to absorb an offensive odor component. The second filter is formed by an ion-exchange
of copper ions of copper carried on a zeolite.
[0008] EPO Application No. 0 508 513 A1 discloses a method for treating diesel fuel engine
exhaust to reduce emission of particulates having cores of carbonaceous material and
condensable hydrocarbons deposited on the carbonaceous material. The condensable hydrocarbons
in the exhaust are contacted with a catalytically active solid acid material having
hydrogen ions releasably retained at acidic sites thereof. The condensable hydrocarbons
in contact with the sites are cracked as hydrogen ions are released from the sites.
The solid acid material is desirably a Y-type zeolite with (H) cations (HY zeolite),
or hydrolyzed multi-valent cations such as lanthanum (LaY zeolite), cerium (CeY zeolite)
and calcium (CaY zeolite) and is supported on a ceramic or metal monolith.
[0009] U.S. Application No. 08/255,289 entitled, "Improved Zeolite-Containing Oxidation
Catalyst and Method of Use" discloses a catalyst composition for treating a diesel
engine exhaust stream containing a volatile organic fraction. The catalyst composition
comprises a refractory carrier on which is disposed a coating of a catalytic material
comprising a catalytically effective amount of ceria having a BET surface area of
at least about 10 m
2/g and a catalytically effective amount of zeolite. It is also known to employ an
alumina stabilized ceria as a support for a platinum group metal as a dual exhaust
catalyst.
[0010] The use of finely divided inorganic oxides containing vanadium and platinum group
metal as active components is disclosed in US Patent No. 5,157,007. The catalyst is
in the form of an open cell, monolith.
[0011] WO 94/22564 discloses a catalyst composition for treating diesel exhaust which includes
ceria and optionally alumina as well as a beta zeolite. A platinum group metal is
employed to promote oxidation of CO and HC while limiting the conversion of SO
2 to SO
3.
[0012] US-A-5 354 720 (corresponding to EP-A-0 559 021) discloses a catalyst for reducing
the quantity of nitrogen oxides in lean exhaust gas of motor vehicle engines, comprising:
an inner structure - reinforcing body; a first catalytic coating on the body, which
coating includes aluminium oxide and/or cerium oxide of large surface area, optionally
stabilised with rare earth metals and/or silicon dioxide as a carrier for catalytically
active noble metal components; and a second catalytic coating of zeolite on the first
catalytic coating; wherein the noble metal components of the first catalytic layer
include iridium and platinum in a ratio by weight of 1:10 to 10:1, and wherein the
zeolite is a temperature - stable zeolite of the mordenite type containing copper
and/or iron.
[0013] As is well-known in the art, catalysts used to treat the exhaust of internal combustion
engines are less effective during periods of relatively low temperature operation,
such as the initial cold-start period of engine operation. This is because the engine
exhaust is not at a temperature sufficiently high for the efficient catalytic conversion
of noxious components in the exhaust. To this end, it is known in the art to employ
high loads of the platinum group metal catalyst to increase catalytic activity at
low temperatures. It is also known to include an adsorbent material, which may be
a zeolite, as part of a catalytic treatment system in order to adsorb gaseous pollutants,
usually hydrocarbons, and retain them during the initial cold-start period until the
exhaust reaches a more suitable, higher temperature. As the exhaust gas temperature
increases, the adsorbed hydrocarbons are driven from the adsorbent and subjected to
catalytic treatment at the higher temperature as disclosed, for example, in U.S. Patent
5,125,231 in which platinum group metal-doped zeolites are employed as low temperature
hydrocarbon adsorbents and oxidation catalysts.
[0014] Such efforts to improve upon the performance of diesel exhaust catalysts have been
problematical. This is because, the low and high temperature operating conditions,
the presence of SO
2 and the need to effectively convert CO and HC to innocuous materials often impose
competing requirements on diesel exhaust catalysts. For example, it is known that
high loading of platinum group metals is required to convert CO and HC at low temperatures.
However, high loading of the platinum group metal increases the rate of conversion
of SO
2 to SO
3.
[0015] It is also known to modify the activity of the platinum group metals by adding appreciable
amounts of vanadium oxide to the catalyst composition. Vanadium oxide reduces the
activity of the platinum metal to thereby reduce the rate at which SO
2 is converted to SO
3. However, after a relatively short operating period, vanadium oxide begins to irreversibly
deactivate the platinum group metal thereby decreasing the performance of the catalyst
in the conversion of CO and HC.
[0016] It would therefore be a significant advance in the art of converting diesel exhaust
to innocuous materials to provide a catalyst which effectively converts CO and HC
including the volatile organic fraction, while minimizing the conversion of SO
2 to SO
3.
Summary of the Invention
[0017] The present invention is generally directed to a catalyst composition, structures
containing the same and methods for oxidizing oxidizable components of a diesel engine
exhaust stream in which at least some of a volatile organic fraction of the diesel
exhaust is converted to innocuous materials and in which gaseous hydrocarbons (HC)
and carbon monoxide (CO) pollutants may also be similarly converted. The operation
of the catalyst composition and the conversion reactions take place without the substantial
conversion of sulfur dioxide (SO
2) to sulfur trioxide (SO
3).
[0018] The catalyst composition for treating a diesel engine exhaust stream specifically
in accordance with the present invention comprises:
a) a catalytically effective amount of at least one platinum group metal on a support
in the presence of at least one catalytic activity controlling compound;
b) a thermally stable ceria; and
c) a non-catalytic pore-containing zeolite.
[0019] In one aspect of the invention, the catalyst composition contains at least one compound
which effectively controls the catalytic activity of the platinum group metal. The
catalyst can therefore be employed in high loading amounts suitable for low temperature
operation while minimizing the conversion of SO
2 to SO
3. Preferred compounds for controlling catalytic activity are compounds containing
vanadium, gold, silver and iron and combinations thereof.
[0020] The present catalyst composition employs a thermally stable ceria which effectively
oxidizes the VOF (volatile organic fraction) of the diesel exhaust. The ceria component
also serves to protect the platinum group metal from contact with the VOF to minimize
the conversion of SO
2 to SO
3 as well as to decrease coke formation.
[0021] In another aspect of the invention the catalyst composition employs a non-catalytic
pore-containing zeolite which absorbs VOF at low temperatures and releases the same
at higher temperatures, but generally below the temperature at which SO
2 converts to SO
3. A particularly preferred zeolite is a hydrogen-beta zeolite.
[0022] The catalyst composition may be applied as a single washcoat or as multiple coats
(e.g. two coats), preferably with the thermally stable ceria as a top coat and the
remaining components within a bottom coat. In this embodiment of the invention the
ceria based top coat has initial contact with the diesel exhaust stream to thereby
absorb the VOF as well as to protect the platinum group metal.
Detailed Description of the Invention
[0023] As used herein and in the claims, the following terms shall have the indicated meanings.
[0024] The term "washcoat" refers to a thin, adherent coating of a material, such as the
catalytic material of the present invention, disposed on the walls forming the parallel
gas flow passages of a carrier, which is typically made of a refractory material such
as cordierite or other oxide or oxide mixture, or a stainless steel.
[0025] The term "thermally stable ceria" means ceria that does not alter its physical structure
at typical diesel exhaust gas temperatures of up to about 700°C.
[0026] The term "bulk form" for ceria means that the ceria is present as discrete particles
(which may be, and usually are, of very small size, e.g., 10 to 20 microns (µm) in
diameter or even smaller) as opposed to having been dispersed in solution form into
another component.
[0027] Catalysts applied to diesel applications must deal with many factors not associated
with gasoline engines. Since the exhaust gas from diesel engines, especially those
equipped with turbochargers, is cool at 150 - 200°C, it is imperative that the catalyst
maintains activity at very low temperatures. Fresh platinum metal catalysts oxidize
CO and HC around 200°C in the presence of SO
2. Until the temperature of the diesel exhaust stream reaches about 200°C, CO and HC
are emitted into the atmosphere.
[0028] As previously described, diesel engine exhaust is comprised of not only CO and unburnt
HC but also a soot phase which includes a volatile organic fraction (VOF) including
unburnt fuel and lubrication oil. The VOF, unless treated in advance, can inactivate
the platinum metal catalyst until temperatures are reached sufficient to oxidize these
materials.
[0029] On the other hand, as temperatures of the exhaust stream rise, the SO
2 tends to oxidize to form S
3O which negatively impacts total particulate matter (TPM) emissions. In particular,
at temperatures above 300°C, the rate at which platinum oxidizes SO
2 to S
3O increases dramatically. Thus, in the operation of diesel engines deactivation of
the catalyst can occur at lower temperatures while unwanted production of SO
3 can occur at higher temperatures. The catalyst composition of the present invention
addresses this problem by a) employing high loading amounts of the platinum group
metal catalyst, b) controlling the activity of the platinum group metal, c) avoiding
deactivation of the platinum group metal, d) storing HC's at lower temperatures in
a non-catalytic environment, and e) minimizing the production of SO
3 when the exhaust stream reaches catalytically active temperatures.
[0030] The catalyst composition of the present invention employs three principal components,
a platinum group metal component on a support including a catalytic activity controlling
compound, a thermally stable ceria and an adsorbent, non-catalytic zeolite. The platinum
group metal component as employed in the present invention is principally responsible
for oxidizing gaseous HC and CO into innocuous materials such as water vapor and carbon
dioxide without significantly catalyzing the conversion of SO
2 to S
3O . The thermally stable ceria functions to oxidize liquid phase HC (VOF) while the
zeolite component adsorbs gaseous HC at low, non-catalytic temperatures and then desorbs
gaseous HC at temperatures generally below the temperature at which a significant
amount of SO
2 converts to SO
3. As a result, the platinum group metal converts HC to innocuous materials without
converting a significant portion of adsorbed SO
2 to SO
3.
[0031] The platinum group metal component of the present invention includes any and all
platinum group metals alone or in combination including oxides thereof. The platinum
group metals include, for example, platinum, palladium, ruthenium, rhodium, iridium
and mixtures and combinations of the same and their oxides. Platinum is the most preferred
of the platinum group metals.
[0032] The amount of platinum group metal employed in the present catalyst composition should
be a high loading quantity to maximize the conversion of CO and HC at the low initial
temperatures of diesel fuel operation. The amount of the platinum group metal is generally
at least about 5 g/ft
3 (0.18 g/dm
3), typically in the range of from about 5 to 100 g/ft
3 (0.18 to 3.53 g/dm
3), most preferably from about 10 to 70 g/ft
3 (0.35 to 2.47 g/dm
3). The catalyst composition of the present invention therefore differs from low loading
compositions in which the platinum group metal is used in much lower quantities, typically
no more than about 2.0 g/ft
3 (0.071 g/dm
3).
[0033] The support for the platinum group metal can be any support which does not tend to
deactivate the platinum group metal during diesel exhaust treatment. Such supports
include, zirconia, titania, silica and combinations thereof, preferably having a relatively
low surface area. The preferred support is alumina, especially alumina having a relatively
low surface area. The reduced surface area of the support serves to control the catalytic
activity of the platinum group metal. While the surface area of the support may vary
from about 50 to 200 m
2/g, the preferred surface area is in the range of from about 90 to 110 m
2/g.
[0034] The platinum group metal component can be prepared, for example, in the manner taught
in Saul G. Hinden, U.S. Patent No. 4,134,860, incorporated herein by reference. A
finely-divided, support (e.g. alumina) is contacted with a solution of a water-soluble,
platinum group metal (e.g. platinum) to provide a composite which is essentially devoid
of free or unabsorbed liquid. The platinum is converted into water-insoluble form
while the composite remains essentially free of unabsorbed liquid. The composite is
comminuted as a slurry to provide solid particles typically in the range of up to
about 15 microns. The composite is then dried and calcined.
[0035] The catalytic component of the present invention is provided with an effective amount
of at least one catalytic activity controlling material. This material serves to control
(e.g. reduce) the catalytic activity of the platinum group metal so that high loadings
of the platinum group metal can be employed for low temperature operations without
a corresponding high conversion rate of adsorbed SO
2 to SO
3.
[0036] While any material which can control the catalytic activity of the platinum group
metal may be used, the preferred materials include compounds containing gold, vanadium,
silver and iron and combinations thereof, such as oxides of gold, vanadium, silver
and iron. The starting materials for forming the catalytic activity controlling compounds
are generally non-chloride, water-soluble compounds such as NaAuSO
3, NH
3VO
3, V
2O
5, AgNO
3 and Fe(NO
3)
3 · 9H
2O, and the like. The amount of the catalytic activity controlling material is typically
in the range of from about 1 to 200 q/ft
3 (0.035 to 7.06 g/dm
3), preferably from about 2 to 50 g/ft
3 (0.071 to 1.77 g/dm
3).
[0037] Thermally stable ceria is employed in the present catalyst composition to adsorb
SO
2 at low temperatures and desorb the SO
2 below the temperature at which the platinum group metal vigorously catalyzes the
conversion of adsorbed SO
2 to SO
3. The ceria component also converts the VOF to innocuous materials. In particular,
the ceria component must adsorb SO
2 under initial engine start up conditions and desorb SO
2 at temperatures below about 300°C. In this way the SO
2 passes through the catalyst system under conditions which do not favor conversion
to SO
3. The amount of the ceria component of the catalyst is typically from about 10 to
60% by weight, preferably from about 20 to 50% by weight, and most preferably from
about 20 to 40% by weight, based on the total weight of the catalyst composition.
[0038] Ceria in bulk form is the preferred thermally stable ceria material for use in the
catalyst composition. Bulk ceria is solid, fine particulate ceria typically having
a particle size distribution such that at least 95% by weight of the particles have
a diameter exceeding 0.5 microns. Further details regarding the structure and function
of bulk ceria can be found in Chung-Zong Wan et al., U.S. Patent No. 4,714,694 incorporated
herein by reference. It will be understood that the ceria component employed in the
present catalyst should be thermally stable at temperatures of the diesel exhaust
stream, typically up to 700°C.
[0039] The zeolite component of the catalyst composition adsorbs and retains gaseous HC
at below catalytic temperatures. The zeolite does not itself catalyze any of the components
of the diesel exhaust stream. Accordingly, the zeolite is non-catalytic and is not
doped with catalytic materials such as platinum, iron and the like. The structure
of the zeolite includes pores or cages which are capable of adsorbing and then desorbing
HC. Desorption of the HC occurs when the diesel exhaust is at a high enough temperature
to impart sufficient energy to the adsorbed HC molecules to enable them to escape
the zeolite pores. Examples of the zeolite material meeting the criteria of the present
invention include, for example, hydrogen-beta zeolite, Y-zeolite, pentasil, mordenite
and mixtures thereof. Hydrogen-beta zeolite is the preferred zeolite. β-zeolites which
may be employed in the present invention are described in Beck,
Zeolite Molecular Sieves, Structure, Chemistry and Use, John Wiley and Sons (1974); Bonetto et al.,
Optimization of Zeolite-Beta in Cracking Catalysts, Influence and Crystallite Size, Applied Catalysis, pp. 37-51 (1992); and U.S. Reissue Patent 28,341 of U.S. Patent
No. 3,308,069; and Newsam et al., Structural Characterization of Zeolite Beta, Proc.
R. Soc. Lond. A 420.375-405 (1988), each of which is incorporated herewith by reference.
[0040] The silica to alumina ratio for β-zeolite is from about 10 to about 200. β-zeolites
are 12-member ring tridirectional zeolites with two types of channels, one being about
7.0 angstroms (0.7 nm) and the other about 5.5 angstroms (0.55 nm). They are known
to have larger pore sizes, high silica to alumina synthesis ratio and a tridirectional
network of pores making them particularly suited for adsorbing HC.
[0041] The range of the amounts of the zeolite component is similar to that of ceria. Typically
the zeolite component is present in an amount from about 10 to 60% by weight, preferably
20 to 50% by weight, most preferably 20 to 40 by weight, based on the total weight
of the catalyst composition.
[0042] The carrier or substrate used in this invention should be relatively inert with respect
to the catalytic composition dispersed thereon. The preferred carriers are comprised
of ceramic-like materials such as cordierite, α-alumina, silicon nitride, zirconia,
mullite, spodumene, alumina-silica-magnesia, zirconium silicate, and refractory metals
such as stainless steel. The carriers are preferably of the type sometimes referred
to as honeycomb or monolithic carriers, comprising a unitary body, usually cylindrical
in configuration, having a plurality of fine, substantially parallel gas flow passages
extending therethrough and connecting both end-faces of the carrier to provide a "flow-through"
type of carrier. Such monolithic carriers may contain up to about 700 or more flow
channels ("cells") per square inch of cross section, although far fewer may be used.
For example, the carrier may have from about 7 to 600, more usually from about 200
to 400, cells per square inch ("cpsi") (108.5 to 9300, more usually 3100 to 6200 cells/dm
2).
[0043] Wall-flow carriers (filters) may also be used. Wall-flow carriers are generally similar
in structure to flow-through carriers, with the distinction that each channel is blocked
at one end of the carrier body, with alternate channels blocked at opposite end-faces.
Wall-flow carrier substrates and the support coatings deposited thereon are necessarily
porous, as the exhaust must pass through the walls of the carrier in order to exit
the carrier structure.
[0044] The catalyst composition is deposited on the carrier such as a monolithic ceramic
material in any conventional manner. A preferred method is to impregnate the carrier
with an aqueous slurry of fine particles of the catalyst composition. This can be
accomplished by dipping the carrier (e.g. wall flow article) into the slurry, removing
excess slurry by draining and subsequent drying at from about 100 to 150°C, followed
by calcining at from about 450 to 600°C.
[0045] The catalyst composition may also be applied to the carrier in multiple coats, typically
as two coats. The composition of the respective coats will depend, in part, on the
type of diesel exhaust being treated. For example, the support can be applied as a
bottom coat and the platinum group metal, the catalytic activity controlling compound,
the ceria and zeolite components as a top coat. The application of a dual coat may
be conducted by first applying a slurry of the support onto the carrier followed by
drying and calcining. The second coat is thereafter applied by first forming a slurry
of the components of the second coat and applying the second coat in the same manner
as the first coat.
[0046] In an embodiment of the invention particularly suited for diesel exhausts having
a high VOF content, the bottom coat of the dual coat application contains the platinum
group metal, the catalytic activity controlling compound, the support and the zeolite
while the top coat contains the thermally stable ceria. By employing ceria as the
top coat, there is a more effective oxidation of VOF and better protection of the
platinum group metal from the deactivating effects of contact with VOF.
[0047] In another embodiment of the catalyst composition of the present invention which
is particularly effective when the diesel exhaust has a dry soot content, the bottom
coat includes the ceria and zeolite components while the top coat contains the platinum
group metal, catalytic activity controlling compound and the support. In other embodiments
of the invention, at least one of the ceria and zeolite components are provided in
each of the coats of the catalyst composition.
EXAMPLE 1
[0048] A catalyst composition according to the present invention was formed by preparing
a first material starting with an ammoniacal solution containing 80% by weight of
the total platinum metal employed in the catalyst composition and combining the same
with 396 g of alumina having a surface area of about 90 m
2/g. The platinum and alumina were pre-mixed followed by the addition of acetic acid
in an amount of 4% by weight based on the weight of the alumina. After mixing, a solution
of ferric nitrate [Fe(NO
3)
3 · 9H
2O], providing a Pt/Fe weight ratio of 10 was added and the combined solution mixed
and ball milled in the presence of added water to give a mixture having a 46% solids
content.
[0049] A second material was prepared by starting with an ammoniacal solution containing
20% by weight of the total platinum metal employed in the catalyst composition. The
platinum solution was combined with bulk ceria in an amount of 396 g and premixed
to form the second material.
[0050] The first and second materials as well as 396 g of H-beta zeolite were blended in
the presence of water to provide a washcoat slurry having a 49% solids content. The
slurry was milled to a mean particle size of less than 8µ. The resulting slurry, having
a solids content of 48 - 49%, a pH of 3.5 to 3.8 and a viscosity of 20 to 30 cps (20
to 30 mPa.s), was coated on a monolithic cordierite substrate (400 cells/in
2) (6200 cells/dm
2) in an amount sufficient to provide a washcoat gain of 1.95 g/in
3 (119 g/dm
3) and then dried at 100 to 150°C and calcined at about 450°C. The final catalyst composition
contained 20 g/ft
3 (0.71 g/dm
3) of platinum and 0.8 g/ft
3 (0.028 g/dm
3) of iron.
EXAMPLE 2
[0051] A slurry containing 600 g of alumina having a surface area of 150 m
2/g, 200 g of bulk ceria and 200 g of H-beta zeolite were blended together to give
a mixture having a solids content of 36%. The mixture was milled so that 90% of the
particles were less than 8µ. The slurry was coated on a monolithic cordierite substrate
(400 cells/in
2) at a washcoat gain of 1.0 g/in
3 (61 g/dm
3), dried at about 100°C and calcined at 450°C to form a bottom catalyst layer.
[0052] A slurry containing platinum metal and vanadium oxide from an ammoniacal solution
was combined with 50 m
2/g titania with the subsequent addition of 15 ml of acetic acid and then milled. The
resulting slurry was combined with 300 g of bulk ceria, 400 g of H-beta zeolite and
100 g of SiO
2 from SiO
2 sol solution and blended together to form a slurry with 90% of the particles having
a particle size of less than 8µ. The slurry was coated onto the above-formed bottom
catalyst layer to form a top catalyst layer having a washcoat gain of 1.5 g/in
3 (91.5 g/dm
3). The coated substrate was dried at 105°C and calcined at 450°C to provide a catalyst
containing 40 g/ft
3 (1.41 g/dm
3) of platinum and 30 g/ft
3 (1.06 g/dm
3) of vanadium.
EXAMPLE 3
[0053] A bottom catalyst layer having the same composition as described in Example 2 was
applied to a monolithic substrate made of cordierite.
[0054] A top catalyst layer slurry was prepared. 427 g of a 25% by weight ZrO
2/SiO
2 composite (210 m
2/g) material was placed in a vessel. An ammoniacal solution of platinum as employed
in Example 1 (14.12 g of platinum) and 0.70 g of gold from a NaAuSO
3 solution were placed in a vessel and diluted to 450 ml with deionized water. The
combined platinum-gold solution was added to the ZrO
2/SiO
2 composite material and mixed to obtain a uniform mixture.
[0055] 15 ml of acetic acid was slowly added to the uniform mixture followed by 20 ml of
formic acid under continuous mixing. The mixed solution was transferred to a ball
mill to which was added 183 g of thermally stable ceria, 244 g of H-beta zeolite,
203 g of SiO
2 sol solution (30% SiO
2) and 925 g of deionized water. The solution was milled until 90% of the particles
had a particle size of less than 8µ.
[0056] The slurry was coated on the bottom catalyst layer at a washcoat gain of 1.5 g/in
3 (91.5 g/dm
3). The substrate was dried at 100°C and calcined at 450°C. The resulting catalyst
contained 40 g/ft
3 (1.41 g/dm
3) of platinum and 2 g/ft
3 (0.071 g/dm
3) of gold.
EXAMPLE 4
[0057] A slurry containing 700 g of alumina having a surface area of 90 m
2/g and 300 g of bulk ceria were blended with water to give a mixture having a solids
content of 38%. The mixture was milled until 90% of the particles had a particle size
of less than 8µ and then coated on a monolithic cordierite substrate (400 cells/in
2) (6200 cells/dm
2) at a washcoat gain of 1.0 g/in
3 (61 g/dm
3), dried at 105°C and calcined at 450°C to form a bottom catalyst layer.
[0058] A mixture of an ammoniacal solution of platinum, a solution of Pd(NH
3)
4(NO
3)
2 and a solution of NaAuSO
3 were combined with 500 g of a ZrO
2/SiO
2 composite and mixed followed by the addition of acetic acid and formic acid.
[0059] The resulting slurry was combined with 300 g of bulk ceria, 600 g of H-beta zeolite,
50 g of Pr
2O
3 and a sufficient amount of water to give a slurry with a 37% solids content. The
slurry was milled until 90% of the particles had a particle size of less than 8 microns.
The slurry was applied to the bottom catalyst layer at a washcoat gain of 1.45 g/in
3 (88.5 g/dm
3), dried at about 105°C and calcined at about 500°C. The resulting catalyst contained
40 g/ft
3 (1.41 g/dm
3) of platinum, 1 g/ft
3 (0.035 g/dm
3) of palladium and 2 g/ft
3 of gold (0.071 g/dm
3).
EXAMPLE 5
[0060] The same bottom catalyst layer described in Example 4 was formed on a monolithic
substrate. A top catalyst layer was formed as described in Example 4 except that the
amount of gold was increased to 5 g/ft
3 (0.177 g/dm
3).
EXAMPLE 6
[0061] 500 g of a 12% TiO
2-Al
2O
3 composite material was mixed with an ammoniacal solution (diluted to 400 ml with
deionized water) containing 14.47 g of platinum. To this mixture was added 15 ml of
acetic acid under mixing.
[0062] A solution of AgNO
3 containing 1.8 g of Ag was diluted to 25 ml with deionized water. The diluted silver
solution was added to the Pt-TiO
2-Al
2O
3 produced above and mixed.
[0063] The mixture was combined with 250 g of H-beta zeolite and 475 g of deionized water.
The resulting slurry was milled until 90% of the particles had a particle size of
less than 8µ.
[0064] A cordierite honeycomb substrate (400 cells/in
2) (6200 cells/dm
2) was coated with the slurry at a washcoat gain of 1.2 g/in
3 (73.2 g/dm
3). The coated substrate was dried at 100°C and calcined at 450°C to form a bottom
catalyst layer.
[0065] A top catalyst layer, prepared in the following manner, was coated on the bottom
catalyst layer.
[0066] 600 g of gamma-alumina, 400 g of bulk ceria, and 1500 ml of deionized water were
combined and milled until 90% of the particles had a particle size of less than 8µ.
The slurry was then coated on the bottom catalyst layer at a washcoat gain of 1.0
g/in
3 (61 g/dm
3). The top coating layer was then dried at 100°C and calcined at 450°C. The resulting
catalyst contained 40 g/ft
3 (1.41 g/dm
3) of platinum and 5 g/ft of silver (0.177 g/dm
3).
EXAMPLE 7
[0067] 438 g of a 25% ZrO
2-SiO
2 composite material was mixed with an ammoniacal solution (diluted to 350 ml with
deionized water) containing 14.47 g of platinum. To this mixture was added 15 ml acetic
acid under mixing.
[0068] A solution of NaAuSO
3 containing 1.81 g Au was diluted to 25 ml with deionized water. The diluted gold
solution was added to the Pt-ZrO
2-SiO
2 produced above and mixed.
[0069] The mixture was combined with 250 g of H-beta zeolite, 250 g of bulk ceria, 310 g
of a 30% solution of SiO
2 and 500 g of deionized water. The resulting slurry was milled until 90% of the particles
had a particle size of less than 8µ.
[0070] A cordierite honeycomb substrate (400 cells/in
2) (6200 cells/dm
2) was coated with the slurry at a washcoat gain of 1.6 g/in
3 (97.6 g/dm
3). The coated substrate was dried at 100°C and calcined at 450°C to form a bottom
catalyst layer.
[0071] A top catalyst layer prepared in the following manner was coated on the bottom catalyst
layer.
[0072] 400 g of a 2% SiO
2 doped titania, 400 g of bulk ceria, 100 g of H-beta zeolite, 500 g of a 30% solution
of SiO
2 and 1100 ml of deionized water were combined and milled until 90% of the particles
had a particle size of less than 8µ. The slurry was then coated on the bottom catalyst
layer at a washcoat gain of 1.0 g/in
3 (61 g/dm
3). The top catalyst layer was then dried at 100°C and calcined at 450°C. The resulting
catalyst contained 40 g/ft
3 (1.41 g/dm
3) of platinum and 5 g/ft
3 (0.177 g/dm
3) of gold.
REFERENCE EXAMPLE 1
[0073] A reference catalyst composition (Ref. Ex. 1) was prepared in the following manner.
[0074] 396 g of gamma-alumina was placed in a vessel and mixed. An ammoniacal solution of
platinum as employed in Example 1 (6.336 g of platinum) was placed in a separate vessel
and diluted to 270 ml with deionized water. The platinum solution was slowly added
to the alumina and mixed followed by the addition of 15 ml of concentrated acetic
acid and further mixing. The resulting solution and 450 g of deionized water were
placed in a ball mill and milled until 90% of the particles had a particle size of
less than 8µ.
[0075] A slurry containing platinum/ceria and H-beta zeolite was prepared in the following
manner.
[0076] 396 g of ceria-zirconia composite material was placed in a vessel and mixed. An ammoniacal
solution of platinum as used in Example 1 (0.704 g of platinum) was placed in a separate
vessel and diluted to 120 ml with deionized water. The platinum solution was added
to the solution of ceria-zirconia and mixed until uniform. 12 ml of concentrated acetic
acid was added to the uniform solution followed by mixing. The resulting solution
as well as 396 g of H-beta zeolite and 650 g of deionized water were placed in a ball
mill and milled until 90% of the particles had a particle size of less than 8µ.
[0077] The two slurries were combined and blended and coated on a cordierite honeycomb substrate
(400 cells/in
2) (6200 cells/dm
2) at a washcoat gain of 1.95 g/in
3 (119 g/dm
3). The substrate was dried at 100°C and calcined at 450°C. The resulting catalyst
contained 20 g/ft
3 (0.71 g/dm
3) of platinum.
[0078] Reference Example 1 and the catalyst composition prepared in accordance with Example
1 were used to treat a diesel exhaust stream containing C
7H
16, C
3H
8, CO, SO
2 and H
2O under the following conditions.
[0079] A reactor synthetic gas having the following composition
200 ppm HC as propylene and propane in
a 2:1 ratio
200 ppm CO
1000 ppm NO
50 ppm SO2
10% by volume H2O (steam)
4.5% by volume CO2
10% by volume O2
balance N2
was provided at a space velocity of 50,000 (volume hour, 1/hr) at an aging temperature
of 500°C for 2 hours in reactor gases. The size of the catalyst was 87 cm
3 with 62 cells/cm
2 (961 cells/dm
2).
[0080] Each of the catalyst compositions were tested over a range of operating temperatures
of from 250°C to 400°C in increments of 50°C. The % conversion of HC, CO and SO
2 were measured by individual analyzers and the results shown in Table 1.
TABLE 1
Temperature |
Ref. Example 1 % Conversion |
|
Example 1 % Conversion |
|
HC |
CO |
SO2 |
|
HC |
CO |
SO2 |
250°C |
62 |
98 |
27 |
|
59 |
96 |
26 |
300°C |
67 |
98 |
31 |
|
63 |
98 |
26 |
350°C |
78 |
98 |
60 |
|
70 |
98 |
48 |
400°C |
81 |
98 |
72 |
|
75 |
98 |
66 |
[0081] As shown in Table 1 the % conversion of SO
2 to SO
3 was significantly lower for the catalyst of Example 1 as compared with Reference
Example 1, particularly at temperatures of 300°C or more. This shows that the catalytic
activity of the platinum metal is effectively controlled in the present invention
to limit the undesirable formation of sulfates. The present catalyst also provides
sufficient conversion rates of HC and CO comparable to that of the reference catalyst.
REFERENCE EXAMPLE 2
[0082] A reference catalyst composition (Ref. Ex. 2) was prepared in the following manner.
[0083] 420 g of gamma-alumina was placed in a vessel and mixed. An ammoniacal solution of
platinum as employed in Example 1 (5.79 g of platinum) was placed in a separate vessel
and diluted to 300 ml with deionized water. The platinum solution was slowly added
to the alumina and mixed followed by the addition of 12 ml of concentration acetic
acid and further mixing. The resulting solution and 300 g of deionized water were
placed in a ball mill and milled until 90% of the particles had a particle size of
less than 8µ.
[0084] A slurry containing platinum/ceria and Fe-beta zeolite was prepared in the following
manner.
[0085] 415 g of alumina doped ceria was placed in a vessel and mixed. An ammoniacal solution
of platinum as used in Example 1 (5.79 g of platinum) was placed in a separate vessel
and diluted to 125 ml with deionized water. The platinum solution was added to the
solution of alumina doped ceria and mixed until uniform. 12 ml of concentrated acetic
acid was added to the uniform solution followed by mixing. The resulting solution
as well as 415 g of Fe-beta zeolite and 700 g of deionized water were placed in a
ball mill and milled until 90% of the particles had a particle size of less than 8µ.
[0086] The two slurries were combined and blended and coated on a cordierite honeycomb substrate
at a washcoat gain of 2.50 g/in
3 (152.6 g/dm
3). The substrate was dried at 100°C and calcined at 450°C. The resulting catalyst
contained 40 g/ft
3 (1.41 g/dm
3) of platinum.
[0087] Reference Example 2 and each of Examples 2 - 4 were used to treat a diesel exhaust
stream containing C
7H
16, CO, SO
2 and H
2O under the same reactor conditions described previously for the comparison of Reference
Example 1 and Example 1. Each of the catalyst compositions were tested over a range
of operating temperatures in 50°C increments of from 200°C to 400°C. The % conversion
at 50°C increments of HC, CO and SO
2 were measured and the results shown in Table 2.
TABLE 2
Temp |
Reference Example 2 % Conversion |
Example 2 % Conversion |
Example 3 % Conversion |
Example 4 % Conversion |
°C |
HC |
CO |
SO2 |
HC |
CO |
SO2 |
HC |
CO |
SO2 |
HC |
CO |
SO2 |
200 |
4 |
98 |
33 |
4 |
94 |
12 |
2 |
98 |
28 |
3 |
97 |
6 |
250 |
46 |
98 |
55 |
23 |
97 |
16 |
28 |
98 |
28 |
27 |
97 |
16 |
300 |
92 |
98 |
55 |
82 |
97 |
20 |
87 |
98 |
41 |
87 |
98 |
46 |
350 |
96 |
99 |
68 |
96 |
98 |
29 |
96 |
98 |
50 |
94 |
98 |
66 |
400 |
97 |
99 |
76 |
97 |
98 |
49 |
97 |
98 |
63 |
95 |
98 |
76 |
[0088] As shown in Table 2, the % conversion of SO
2 to SO
3 for the present catalyst composition is significantly less than the reference catalyst
especially at low operating temperatures.
[0089] Reference Example 1 and each of Examples 5 and 6 were used to treat the same diesel
exhaust stream under the same reactor conditions as previously described above for
Examples 2 - 4. Each of the catalyst compositions were measured for HC, CO and SO
2 conversion rates in the same manner as described above and the results are shown
in Table 3.
TABLE 3
Temp. °C |
Reference Example 2 % Conversion |
|
Example 5 % Conversion |
|
Example 6 % Conversion |
|
HC |
CO |
SO2 |
|
HC |
CO |
SO2 |
|
HC |
CO |
SO2 |
200 |
4 |
98 |
33 |
|
2 |
91 |
12 |
|
1 |
83 |
6 |
250 |
46 |
98 |
55 |
|
19 |
97 |
15 |
|
3 |
91 |
8 |
300 |
92 |
98 |
55 |
|
73 |
97 |
33 |
|
31 |
97 |
8 |
350 |
96 |
99 |
68 |
|
91 |
97 |
53 |
|
85 |
98 |
11 |
400 |
97 |
99 |
76 |
|
93 |
97 |
67 |
|
93 |
98 |
27 |
[0090] As shown in Table 3, the % conversion of SO
2 to SO
3 for the present catalyst composition is significantly less than the reference catalyst.
[0091] Reference catalyst 2 and the catalyst of Example 7 were subjected to a diesel engine
light-off activity test in the following manner.
[0092] A cordierite honeycomb substrate having a volume of 55 in
3 (901.3cm
3), and 400 cells/in
2 (6200 cells/dm
2), was loaded with the respective catalysts having a platinum loading of 40 g/ft
3 (1.41 g/dm
3). The catalyst structures were contacted with a diesel exhaust stream from a diesel
engine operating at a speed effective to provide 2000 l/min of exhaust, an engine
load of 15 - 180 NM and a catalyst inlet temperature ranging from 100 to 530°C. The
engine aging cycle was 130°C for 15 minutes followed by 650°C for 15 minutes.
[0093] The percentage conversion of HC, CO and total particulate matter (TPM) was measured
and the results are shown in Table 4.
TABLE 4
Temp. °C |
% HC Conv. |
% CO Conv. |
% TPM Conv. |
|
Ref. 2 |
Ex. 7 |
Ref. 2 |
Ex. 7 |
Ref. 2 |
Ex. 7 |
150 |
58 |
48 |
7 |
5 |
45 |
55 |
200 |
41 |
92 |
11 |
5 |
66 |
71 |
250 |
57 |
70 |
86 |
78 |
50 |
55 |
300 |
79 |
82 |
86 |
95 |
40 |
59 |
350 |
78 |
76 |
72 |
94 |
11 |
19 |
400 |
71 |
65 |
76 |
91 |
5 |
16 |
450 |
72 |
60 |
75 |
92 |
-10 |
18 |
500 |
80 |
57 |
74 |
93 |
-30 |
25 |
[0094] As shown in Table 4, the conversion of TPM for the present catalyst composition was
significantly greater than for the reference catalyst, especially at high operating
temperatures while the present catalyst exhibited sufficient conversion rates of HC
and CO although somewhat less than the reference catalyst.
1. A catalyst composition for treating a diesel engine exhaust stream comprising hydrocarbons,
the composition comprising:
a) at least one platinum group metal on a support in the presence of at least one
catalyst activity controlling compound selected from the group consisting of gold,
vanadium, silver and iron compounds;
b) a thermally stable ceria; and
c) a zeolite to adsorb and desorb hydrocarbons and which is not doped with a catalytic
material.
2. The catalyst composition of claim 1 wherein the zeolite is selected from the group
consisting of hydrogen-beta zeolite, Y zeolite, pentasil, mordenite and mixtures thereof.
3. The catalyst composition of claim 1 wherein the amount of the catalyst activity controlling
compound is from about 1 to 200 g/ft3 (0.0353 to 7.063 g/dm3).
4. The catalyst composition of claim 1 wherein the amount of the catalyst activity controlling
compounds is from about 2 to 50 g/ft3 (0.071 to 1.77 g/dm3).
5. The catalyst composition of claim 1 wherein the amount of the platinum group metal
is at least about 5 g/ft3 (0.177 g/dm3).
6. The catalyst composition of claim 1 wherein the amount of the platinum group metal
is from about 5 to 100 g/ft3 (0.177 to 3.53 g/dm3).
7. The catalyst composition of claim 1 wherein the amount of the platinum group metal
is from about 10 to 70 g/ft3 (0.353 to 2.47 g/dm3).
8. The catalyst composition of claim 1 wherein the support for the platinum group metal
is selected from the group consisting of alumina, zirconia, titania, silica and combinations
thereof.
9. The catalyst composition of claim 1 wherein the support for the platinum group metal
is alumina.
10. The catalyst composition of claim 1 wherein the support comprises alumina.
11. The catalyst composition of claim 1 wherein the surface area of the support is from
about 50 to 200 m2/g.
12. The catalyst composition of claim 10 wherein the surface area of the support is from
about 90 to 110 m2/g.
13. The catalyst composition of claim 1 wherein the thermally stable ceria comprises bulk
form ceria composed of fine particles wherein 95% by weight of the particles has a
diameter exceeding 0.5µ.
14. The catalyst composition of claim 1 wherein the amount of the thermally stable ceria
is from about 10 to 60% by weight based on the total weight of the catalyst composition.
15. The catalyst composition of claim 1 wherein the ceria is in the form of bulk ceria.
16. The catalyst composition of claim 1 wherein the zeolite is hydrogen-beta zeolite.
17. The catalyst composition of claim 1 wherein the amount of the zeolite is from about
10 to 60% by weight based on the total weight of the catalyst composition.
18. The catalyst composition of claim 1 wherein the platinum group metal is platinum.
19. A catalyst structure comprising:
a) a catalyst substrate; and
b) the catalyst composition of claim 1 on said substrate.
20. The catalyst structure of claim 19 wherein the substrate is in the form of a flow-through
carrier.
21. The catalyst structure of claim 19 wherein the substrate is in the form of a wall-flow
carrier.
22. The catalyst structure of claim 19 wherein the catalyst composition is in the form
of at least one washcoat.
23. The catalyst structure of claim 19 wherein the catalyst composition is in the form
of two washcoats, a bottom washcoat comprising the support and a top washcoat comprising
the platinum group metal, the catalytic activity controlling compound, the thermally
stable ceria and the non-catalytic pore-containing zeolite.
24. The catalyst structure of claim 19 wherein the catalyst composition is in the form
of two washcoats, a bottom washcoat comprising the platinum group metal, the catalytic
activity controlling compound, the support and the non-catalytic pore-containing zeolite
and a top washcoat comprising the thermally stable ceria.
25. The catalyst structure of claim 19 wherein the catalyst composition is in the form
of two washcoats, a bottom washcoat comprising the thermally stable ceria and the
non-catalytic pore-containing zeolite and a top washcoat comprising the platinum group
metal, the catalytic activity controlling compound and the support.
26. The catalyst structure of claim 19 wherein the catalyst composition is in the form
of two washcoats, each coat containing at least one of said thermally stable ceria
and said zeolite.
27. A method of treating a diesel exhaust stream comprising passing said diesel exhaust
stream into operative contact with the catalyst composition of claim 1.
28. A method of treating a diesel exhaust stream comprising passing said diesel exhaust
stream into operative contact with the catalyst structure of claim 19.
1. Katalysatorzusammensetzung zur Behandlung des Abgasstroms eines Dieselmotors umfassend
Kohlenwasserstoffe, wobei die Zusammensetzung umfasst:
a) wenigstens ein Platinmetall auf einem Träger in Anwesenheit wenigstens einer die
Katalysatoraktivität steuernden Verbindung, gewählt aus der Gruppe bestehend aus Gold-,
Vanadium-, Silber- und Eisenverbindungen;
b) ein thermisch stabiles Cerdioxid;
c) ein Zeolith um Kohlenwasserstoffe zu adsorbieren und desorbieren und welches nicht
mit einem katalytischen Material dotiert ist.
2. Katalysatorzusammensetzung nach Anspruch 1, wobei der Zeolith aus der Gruppe gewählt
ist, bestehend aus Wasserstoff- Beta-Zeolith, Y-Zeolith, Pentasil, Mordenit und deren
Mischungen.
3. Katalysatorzusammensetzung nach Anspruch 1, wobei die Menge der die Katalysatoraktivität
steuernden Verbindung zwischen 1 bis 200 g/ft3 (0,0353 bis 7,063 g/dm3) beträgt.
4. Katalysatorzusammensetzung nach Anspruch 1, wobei die Menge der die Katalysatoraktivität
steuernden Verbindung zwischen 2 bis 50 g/ft3 (0,071 bis 1,77 g/dm3) beträgt.
5. Katalysatorzusammensetzung nach Anspruch 1, wobei die Menge des Platinmetalls wenigstens
ungefähr 5 g/ft3 (0,177 g/dm3) beträgt.
6. Katalysatorzusammensetzung nach Anspruch 1, wobei die Menge des Platinmetalls von
ungefähr 5 bis 100 g/ft3 (0,177 bis 3,53 g/dm3) beträgt.
7. Katalysatorzusammensetzung nach Anspruch 1, wobei die Menge des Platinmetalls von
ungefähr 10 bis 70 g/ ft3 (0,353 to 2,47 / dm3) beträgt.
8. Katalysatorzusammensetzung nach Anspruch 1, wobei der Träger für das Platinmetall
aus der Gruppe gewählt ist, bestehend aus Aluminiumoxid, Zirkoniumdioxid, Titanerde,
Siliziumdioxid und deren Kombinationen.
9. Katalysatorzusammensetzung nach Anspruch 1, wobei der Träger des Platinmetalls Aluminiumoxid
ist.
10. Katalysatorzusammensetzung nach Anspruch 1, wobei der Träger Aluminiumoxid umfasst.
11. Katalysatorzusammensetzung nach Anspruch 1, wobei die Mantelfläche des Trägers von
ungefähr 50 bis 200 m2/g beträgt.
12. Katalysatorzusammensetzung nach Anspruch 1, wobei die Mantelfläche des Trägers von
ungefähr 90 bis 110 m2/g beträgt.
13. Katalysatorzusammensetzung nach Anspruch 1, wobei das thermisch stabile Cerdioxid
Cerdioxid in der Form von Schüttgut (bulk form ceria) umfasst, bestehend aus feinen
Teilchen, wobei 95 Gew.-% der Teilchen einen Durchmesser aufweisen, der 0,5 µm überschreitet.
14. Katalysatorzusammensetzung nach Anspruch 1, wobei die Menge des thermisch stabilen
Cerdioxid von ungefähr 10 bis 60 Gew.-% bezogen auf das Gesamtgewicht der Katalysatorzusammensetzung
beträgt.
15. Katalysatorzusammensetzung nach Anspruch 1, wobei das Cerdioxid in der Form von Cerdioxidschüttgut
vorliegt.
16. Katalysatorzusammensetzung nach Anspruch 1, wobei das Zeolith Wasserstoff-Beta-Zeolith
ist.
17. Katalysatorzusammensetzung nach Anspruch 1, wobei die Menge des Zeoliths von 10 bis
60 Gew.-% bezogen auf das Gesamtgewicht der Katalysatorzusammensetzung beträgt.
18. Katalysatorzusammensetzung nach Anspruch 1, wobei das Platinmetall Platin ist.
19. Katalysatorstruktur bzw. -aufbau umfassend:
a) ein Katalysatorsubstrat; und
b) die Katalysatorzusammensetzung aus Anspruch 1 auf dem Substrat.
20. Katalysatorstruktur bzw. -aufbau nach Anspruch 19, wobei das Substrat in der Form
eines Durchflussträgers vorliegt.
21. Katalysatorstruktur bzw. -aufbau nach Anspruch 19, wobei das Substrat in Form eines
Wanddurchflussträgers (wall flow carrier) vorliegt.
22. Katalysatorstruktur bzw. -aufbau nach Anspruch 19, wobei die Katalysatorzusammensetzung
in Form wenigstens eines Washcoats vorliegt.
23. Katalysatorstruktur bzw. -aufbau nach Anspruch 19, wobei die Katalysatorzusammensetzung
in Form zweier Washcoats vorliegt, eines unteren Washcoats, welcher den Träger umfasst,
und eines oberen Washcoats, welcher das Platinmetall umfasst, die die katalytische
Aktivität steuernde Verbindung, das thermisch stabile Cerdioxid und das nichtkatalytische,
Poren aufweisende Zeolith.
24. Katalysatorstruktur bzw. -aufbau nach Anspruch 19, wobei die Katalysatorzusammensetzung
in Form zweier Wash-Coats vorliegt, eines Boden-Wash-Coats, umfassend das Metall der
Platingruppe, die die katalytische Aktivität steuernde Verbindung, den und das nichtkatalytische
Poren aufweisende Zeolith und eines oberen Wash-Coats, umfassend das thermisch stabile
Cerdioxid.
25. Katalysatorstruktur nach Anspruch 19, wobei die Katalysatorzusammensetzung in Form
zweier Wasch- Coats vorliegt, eines Boden-Wash-Coats, umfassend das thermisch stabile
Cerdioxid und das nichtkatalytische Poren aufweisende Zeolith und eines oberen Wash-Coats,
umfassend das Platinmetall, die die katalytische Aktivität steuernde Verbindung und
den Träger.
26. Katalysatorstruktur nach Anspruch 19, wobei die Katalysatorzusammensetzung in Form
zweier Wash-Coats vorliegt, wobei jede Beschichtung wenigstens eines des thermisch
stabilen Cerdioxids und des Zeoliths enthält.
27. Verfahren zur Behandlung eines Dieselabgasstroms, umfassend das Durchführen des Dieselabgasstroms
in operativem Kontakt mit der Katalysatorzusammensetzung nach Anspruch 1.
28. Verfahren zur Behandlung eines Dieselabgasstromes, umfassend das Durchführen des Dieselabgasstromes
in operativen Kontakt mit der Katalysatorstruktur bzw. -aufbau nach Anspruch 19.
1. Une composition de catalyseur pour le traitement d'un courant d'échappement de moteur
diesel comportant des hydrocarbures, la composition comportant :
a) au moins un groupe de métal du platine sur un support en présence d'au moins un
composé contrôlant l'activité du catalyseur, choisi dans le groupe constitué de composés
d'or, de vanadium, d'argent et de fer ;
b) une cérite thermiquement stable ; et
c) une zéolite pour adsorber et désorber des hydrocarbures et qui n'est pas dopée
au moyen d'un matériau catalytique.
2. La composition de catalyseur de la revendication 1, dans laquelle la zéolite est choisie
dans le groupe constituée d'une zéolite béta-hydrogénée, d'une zéolite Y, de pentasil,
de mordénite et de mélanges de ceux-ci.
3. La composition de catalyseur de la revendication 1, dans laquelle la quantité de composé
contrôlant l'activité du catalyseur est d'environ 1 à 200 g/pied3 (0,0353 à 7,063 g/dm3).
4. La composition de catalyseur de la revendication 1, dans laquelle la quantité de composé
contrôlant l'activité du catalyseur est de 2 à 50 g/pied3 (0,071 à 1,77 g/dm3).
5. La composition de catalyseur de la revendication 1, dans laquelle la quantité de métal
du groupe du platine est d'au moins environ 5 g/pied3 (0,177 g/dm3).
6. La composition de catalyseur de la revendication 1, dans laquelle la quantité de métal
du groupe du platine est d'environ 5 g/pied3 à 100 g/pied3 (0,177 g. à 3,53 g/dm3).
7. La composition de catalyseur de la revendication 1, dans laquelle la quantité de métal
du groupe du platine est d'environ 10 à 70 g/pied3 (0,353 à 2,47 g/dm3).
8. La composition de catalyseur de la revendication 1, dans laquelle le support pour
le métal du groupe de platine est choisi dans le groupe constitué de l'alumine, de
la zircone, du dioxyde de titane, de la silice et des combinaisons de ceux-ci.
9. La composition de catalyseur de la revendication 1, dans laquelle le support du métal
du groupe du platine est l'alumine.
10. La composition de catalyseur de la revendication 1, dans laquelle le support comporte
de l'alumine.
11. La composition de catalyseur de la revendication 1, dans laquelle la surface spécifique
du support est d'environ 50 à 200 m2/g.
12. La composition de catalyseur de la revendication 10, dans laquelle la surface spécifique
du support est d'environ 90 à 110 m2/g.
13. La composition de catalyseur de la revendication 1, dans laquelle la cérite thermiquement
stable comporte une cérite, sous forme brute, composée de fines particules dans laquelle
95 % en poids des particules ont un diamètre supérieur à 0,5 µ.
14. La composition de catalyseur de la revendication 1, dans laquelle la quantité de cérite
thermiquement stable est d'environ 10 à 60 % en poids, en se basant sur le poids total
de la composition de catalyseur.
15. La composition de catalyseur de la revendication 1, dans laquelle la cérite est sous
la forme de cérite brute.
16. La composition de catalyseur de la revendication 1, dans laquelle la zéolite est une
zéolite béta hydrogénée.
17. La composition de catalyseur de la revendication 1, dans laquelle la quantité de zéolite
est d'environ 10 à 60 % en poids en se basant sur le poids total de la composition
de catalyseur.
18. La composition de catalyseur de la revendication 1, dans laquelle le métal du groupe
de platine est le platine.
19. Une structure de catalyseur comportant :
a) un substrat de catalyseur ; et
b) la composition de catalyseur de la revendication 1 sur ledit substrat.
20. La structure de catalyseur de la revendication 19, dans laquelle le substrat est sous
la forme d'un support à écoulement transversal.
21. La structure de catalyseur de la revendication 19, dans laquelle le substrat est sous
la forme d'un support à écoulement lamellaire.
22. La structure de catalyseur de la revendication 19, dans laquelle la composition du
catalyseur est sous la forme d'au moins une couche de lavage.
23. La structure de catalyseur de la revendication 19, dans laquelle la composition du
catalyseur est sous la forme de deux couches de lavage, une couche inférieure de lavage
comportant un support et une couche supérieure de lavage comportant le métal du groupe
du platine, le composé contrôlant l'activité du catalyseur, la cérite thermiquement
stable et la zéolite non catalytique renfermant des pores.
24. La structure catalytique de la revendication 19, dans laquelle la composition de catalyseur
est formée de deux couches de lavage, une couche de lavage inférieure comportant du
métal du groupe du platine, le composé contrôlant l'activité du catalyseur, le support
et la zéolite non-catalytique renfermant des pores et une couche de lavage supérieure
comprenant la cérite thermiquement stable.
25. La structure de catalyseur de la revendication 19, dans laquelle la composition de
catalyseur est sous la forme de deux couches de lavage, une couche de lavage inférieure
comportant la cérite thermiquement stable et la zéolite non-catalytique renfermant
des pores et une couche de lavage supérieure comportant le métal du groupe du platine,
le composé contrôlant l'activité catalytique et le support.
26. La structure de catalyseur de la revendication 19, dans laquelle la composition de
catalyseur est sous la forme de deux couches de lavage, chaque couche comprenant au
moins une parmi ladite cérite thermiquement stable et ladite zéolite.
27. Procédé pour traiter un courant d'échappement diesel, comportant le passage dudit
courant d'échappement diesel en contact de fonctionnement avec la composition de catalyseur
de la revendication 1.
28. Procédé pour traiter un courant d'échappement diesel comportant le passage dudit courant
d'échappement diesel en contact de fonctionnement avec la structure de catalyseur
de la revendication 19.